<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .box {
      color: white;

      background-color: rgb(100, 100, 100);
      background-color: #646464;

      background-color: rgb(0, 0, 0);
      background-color: #000000;

      background-color: rgc(255, 255, 255);
      background-color: #FFFFFF;

      background-color: #e1251b;

    }
  </style>
</head>

<body>
  <div class="box">哈哈哈</div>
</body>

</html>